Issue 5275 - Minimize memory usage as soon as possible

include/AdblockPlus/JsEngine.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 295 matching lines @@
     void SetGlobalProperty(const std::string& name, const AdblockPlus::JsValue& value);
 
     /**
      * Returns a pointer to associated v8::Isolate.
      */
     v8::Isolate* GetIsolate()
     {
       return isolate->Get();
     }
 
+    /**
+     * Notifies JS engine about critically low memory what should cause a
+     * garbage collection.
+     */
+    void NotifyLowMemory();
   private:
     void CallTimerTask(const JsWeakValuesID& timerParamsID);
 
     explicit JsEngine(const ScopedV8IsolatePtr& isolate, TimerPtr timer, WebRequestPtr webRequest);
 
     JsValue GetGlobalObject();
 
     /// Isolate must be disposed only after disposing of all objects which are
     /// using it.
     ScopedV8IsolatePtr isolate;
 
     FileSystemPtr fileSystem;
     LogSystemPtr logSystem;
     std::unique_ptr<v8::Persistent<v8::Context>> context;
     EventMap eventCallbacks;
     std::mutex eventCallbacksMutex;
     JsWeakValuesLists jsWeakValuesLists;
     std::mutex jsWeakValuesListsMutex;
     TimerPtr timer;
     WebRequestPtr webRequest;
     WebRequestSharedPtr webRequestLegacy;
   };
 }
 
 #endif